Rarity within taxonomic lineages and the use of taxa above the level of species

Studies which attempt to explain rarity within lineages are becoming increa singly popular. An ability to explain causative factors for rarity based on shared characteristics is an intuitively attractive concept, since it may greatly reduce the number of studies needed to understand rarity in all spe cies. Most studies have used the taxonomic unit of family as the lever at w hich patterns in the distribution of rarity are examined, though no justifi cation for the use of family has been provided. To date, no evidence has be en produced to show that family-based patterns represent patterns at lower taxonomic levels. To test whether family-based levels of rarity reliably reflected generic le vels. I compared the incidence of rarity within 114 genera from 47 families . 113 genera (> 99%) within 46 families showed no difference from family me ans in the proportion of rare species they contained, indicating that the i ncidence of rarity is consistent between the taxonomic levels of family and genus. This result suggests family level patterns reflect pattern at lower taxonomic levels and supports the use of family as an appropriate level to investigate patterns in the distribution of rarity within a flora.